MOLLUSCAN LARV^ 



435 



an olfactory organ or osphradiiim. The sexes are separate 

 or united. There are two common larval stages — the 



Fig. 248. — Stages in molluscan development. 



I. Larva of Heteropod (after Gegenbaur) ; sh., shell covering visceral 



hump ; v., vehim ; /., foot. 

 II. Larva of Atlanta (after Gegenbaur) ; v., velum ; sh., shell ; /., foot ; 

 op., operculum. 



Trochosphere, which resembles the same stage in some 

 Annelids, and the more characteristic Veliger (Fig. 248) ; 

 but the development is often direct. 



